As motor vehicle configuration transitions from internal combustion engine to hybrid combinations of internal combustion engine and electric motor to all electric motor drive vehicles, a greater dependence on electric power generation and storage must evolve to match the demands placed on the vehicle's performance.
There are many sources of energy available for conversion to electricity to be used as generated or for storage on board the vehicle until needed to meet demand. These known sources and undeveloped sources will generate electricity as alternating current or direct current. Alternating current generation will vary by power and frequency while direct current will vary by power output.
As with the major power grids, these varying output systems must be made to link to a common grid in order to make generated power available for distribution to systems that require electricity to function.
To this end, it is appropriate to propose a methodology for creating the means to capture these various sources of electrical power, establish a common-denominator means to condition these various sources to a common mode so that a practical bidirectional grid may be efficiently used to capture electrical power generated and distributed for use or storage depending on the mobile vehicle's demand.
To be clear: this is not a vehicle-based mobile electric power system; i.e., a power system transported to a site by a vehicle where no power is available from a utility or stationary generator. It is an onboard power generating use and storage system whose primary mission is to provide electrical power to the vehicle. It is an onboard electrical power station or energy center or plant. By its size, it can be described as a microgrid.
Historically, the demand for electrical power for internal combustion engine motor vehicles has increased steadily. From 1950 to 1980, for example, required generator/alternator output increased by about 500%. For the foreseeable future, this demand will continue to increase due to the growing amount of onboard electrical equipment that has become an integral part of every new vehicle design for safety, comfort and convenience.
For current internal combustion engine motor vehicles, with the engine stopped, the battery is the vehicle's energy store and, with the engine running, the alternator becomes the onboard electrical generating plant. For trouble-free generation, it is necessary that alternator output, battery capacity, starter power requirements and electricity consuming loads are matched and optimized.
In a normal driving cycle, the battery must always have sufficient charge so that the motor vehicle can be restarted, despite the needs for critical safety and security systems continuous functionality. With the vehicle parked, electrically consuming loads should continue to operate for a reasonable period without discharging the battery to the extent that the vehicle cannot be restarted.
The conventional lead-acid storage battery used in motor vehicles led to the development of the direct current (DC) generator. A DC generator was required in order to recharge the battery, a DC device. Because the early motor vehicles depended on DC batteries, any electrical equipment for these early motor vehicles operated off DC supplies.
Until the middle of the seventies, most vehicles were equipped with DC generators. Today, DC generators have been replaced by alternators that internally generate alternating current (AC) power that is then rectified into DC output. It was the development of cost effective diodes in the sixties that allowed their adoption for use in alternators that replaced DC generators.
DC generators were not as reliable as alternators and were not able to meet continuous charge and electrical accessory requirements over the variable engine speeds from engine idling to highway speeds. Alternators are much more able to provide stable output over the operating range with a much longer vehicle service life, low weight, higher compactness and high electrical efficiency. As the demand for onboard electrical energy increases, manufacturers can increase the size and output characteristics of alternators. Within physical limits, aftermarket upgraded alternators can be installed to help address additional electrical power demands.
Motor vehicle electrical consuming loads have differing duty cycles. The types of loads are divided between continuous loads, long duty cycle loads and short duty cycle loads. As motor vehicles transition from full internal combustion engine through hybrid combinations to full electric, the ability to sustain operation with the reduced reliance on onboard batteries that add significant weight to the vehicle, particularly lead-acid types, becomes problematical.
As the internal combustion engine motor vehicle gives way to hybrid electric and fully electric motor vehicles, the storage of power and power generating systems will have to incorporate more sources of power generation and storage to replace the energy sources commonly used with internal combustion engine motor vehicles. Current onboard electrical power systems or subsystems are insufficient to sustain long-distance travel for full electric vehicles or internal combustion engine hybrid vehicles with supplemental direct drive traction motor.
The microgrid electrical system described here envisions multiple onboard electrical power generating and energy storage systems that must be able to be joined to a motor vehicle mobile micro grid that redistributes this generated and stored power to vehicle electrical consuming devices and systems. Each of these devices or subsystems must be controlled through a controller network that is parallel to the device and subsystems network.
It is envisioned that all sources of electrical power, whether AC or DC, be conditioned to a high voltage DC buss. The interconnect distribution wiring infrastructure can be designed for economic benefit without significant sacrifice of efficiency. An electrical transmission grid is a network of power sources, transmission conditioners, transmission busses, storage devices and electromechanical devices that require electricity to function. DC transmission does not result in reactive losses as with AC transmission. Transfers of energy from renewable sources on the vehicle are intermittent and, by nature, have wide dynamic ranges, so that the interface must be DC.
For example, solar photovoltaic panels or small wind turbines depend on climatic conditions to operate and produce electrical energy. When operating alone, they can be poor sources of power. However, systems that merge sources, such as wind, sun and other renewable sources, produce more effective energy. The system proposed here constitutes a distributive source of power, distributed by DC busses to a distributed group of electrical consuming or storage devices and systems. Each device or subsystem represents a node on the microgrid buss.
Electrical power is always subject to losses in transmission whether for short distances between components on a printed circuit board or over long distance high voltage lines. The major contributor to power loss in transmission is I2R losses (Joule losses):Ploss=I2R
Since the power, P, is the product of current, I, and voltage, V,I=P/V Therefore,Ploss=(P/V)2R=(P2/V2)R 
Power loss is proportional to transmission line resistance and inversely proportional to the square of the transmission voltage. Therefore, power loss is minimized by low resistance and high voltage.
For intrastate and interstate grids, high voltage direct current transmission is not uncommon.